Is it typical, even at very high Q, that signal is passed uneffected (well, at lower volume)? I thought that if the Q was reasonably high, it would provide enough DB loss for the outer frequencies that it would drown them out, particularly with guitar. Does adding more bandpasses in series fix this?
-Colin
Sounds like something's not right. At very high Q, the effect should be pretty noticable. If it's high enough, it'll oscillate all by itself.
Quote from: Tim EscobedoSounds like something's not right. At very high Q, the effect should be pretty noticable. If it's high enough, it'll oscillate all by itself.
Right-o, it certainly oscillates when I get the Q high enough, and the effect is totally noticeable. The question is, should there always be leakthrough even with a high Q?
-Colin
At high Q, audio in the passband will be at the output. But you should be able to notice a tonal effect. What schem are you using?
I don't think you're quite understanding my question. The effect is very noticeable, and it's clearly working as a bandpass filter, with reasonably high Q. My question is, is it normal that even at high Q a small amount of unneffected signal will pass through because the out-of-pass-band-lower-gain doesn't drop it off enough?
I'm using a design I've cooked up based on some envelope filter schematics. I'll draw it up tonight.
-Colin
Maybe the bandwidth is too large?
:shock: I have no knowledge bout htese but in a building list. Just have wondered if you make classic state-variable like epfm super tone control does the Q effect just bandpass output or is it noticed at lo and hi pass output as well? :shock:
Colin!
The simple answer is "YES", you can't get a analog filter with infinitely steep "shoulders". So there will always be some bleed-thro.
Unless you go digital...
Kindest regards, Bernt.
QuoteIs it typical, even at very high Q, that signal is passed uneffected (well, at lower volume)? .... The question is, should there always be leakthrough even with a high Q?
Yes. Active filters, unlike LC filters, have an initial slope of whatever they're designed to do, but then at some lower level - like maybe -20 to -40db - the signal declines at only a single time constant slope of -6db per octave. You have to stack successive active filters to clear away the down-slope signal even more.
Quoteif you make classic state-variable like epfm super tone control does the Q effect just bandpass output or is it noticed at lo and hi pass output as well?
The "Q" has an effect on low and high pass as well, although it's a bit funny talking about the "Q" of a non-bandpass filter when Q is commonly used to talk about bandwidth.
A simple lowpass filter with a high Q will have a resonant peak at the frequency where the response would be half power if the Q were 1. So the frequency response is flat to nearly the falloff frequency, then rises to a resonant peak, then falls dramatically into the stop band. The reverse happens with a high Q high pass filter. A state variable does exactly this - if the bandpass is high Q, so are the lo and high pass sections.
Interestingly enough, a good wah pedal is usually a high Q lowpass filter. The passband below the resonant peak lets the lower part of the signal through for a fuller sound and the peak adds the resonant interest.
depends what U R feeding it.
Sine? Square?
If U R feeding it a sine(wave), all signal will B booted.
Amplitue Enhancement.
If it's a MultiMode, & use notch, the sine will (escentially)dissappear.
If U R using Square(wave) there are still harmonics left outside
the passband in bandpass OR notch.
So the signal will never completely dissappear.
Hopethishelps
tone
:) Thanks R.G. :)
Thanks RG, Bernt! I was wondering if my circuit was messed up... I'll draw it up later tonight for all of you kind folkses.
-Colin